LED Wavelength Conversion via Segmented InGaN Quantum Wells
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current LEDs emitting green and red light using GaN/InGaN quantum wells face inefficiencies due to degradation of InGaN quality and low light absorption, leading to poor conversion efficiencies, especially when high indium concentrations are required for wavelength conversion.
Innovation Solution
A light-emitting diode structure with a p-n junction and a conversion structure featuring quantum wells and absorption layers with specific indium concentrations, where the indium concentration in the absorption layers is lower than in the emissive layers, and separated by GaN interlayers to maintain semiconductor quality and enhance light absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the indium concentration in the emissive layers is increased to achieve green or red light emission, then the emission wavelength shifts to longer wavelengths, but the quality of InGaN degrades due to increased lattice parameter difference with GaN
Solution Approach 1:
The conversion layers are segmented into multiple quantum wells with thin InGaN emissive layers (3 nm thickness) separated by GaN barrier layers. This segmentation allows achieving the required absorption while maintaining material quality, as each thin layer remains within the acceptable indium concentration limit despite the total thickness being large (at least 20 quantum wells).
Solution Approach 2:
Different regions of the conversion structure have different indium concentrations optimized for their specific functions: the emissive layers have high indium concentration (25-40%) for wavelength conversion, while the barrier layers have low indium concentration for maintaining crystal quality and lattice matching with the substrate.
2Productivity
If the thickness of InGaN emissive layers in conversion layers is increased to improve blue light absorption, then light absorption improves, but the quality of InGaN degrades
Solution Approach 1:
The conversion layers are segmented into multiple quantum wells with thin InGaN emissive layers (3 nm thickness) separated by GaN barrier layers. This segmentation allows achieving the required absorption while maintaining material quality, as each thin layer remains within the acceptable indium concentration limit despite the total thickness being large (at least 20 quantum wells).
Solution Approach 2:
Multiple thin InGaN layers are combined in series within the conversion structure to achieve the equivalent absorption of a single thick layer, while avoiding the quality degradation that would result from any single thick layer. The cumulative thickness of all InGaN layers provides sufficient absorption without compromising individual layer quality.
3Productivity
If a large number of quantum wells are used in conversion layers to achieve at least 80% conversion of blue light, then light absorption improves, but the quality of InGaN degrades and reabsorption problems occur
Solution Approach 1:
The conversion layers are segmented into multiple quantum wells with thin InGaN emissive layers (3 nm thickness) separated by GaN barrier layers. This segmentation allows achieving the required absorption while maintaining material quality, as each thin layer remains within the acceptable indium concentration limit despite the total thickness being large (at least 20 quantum wells).
Solution Approach 2:
GaN barrier layers act as intermediary structures between adjacent InGaN emissive layers. These barrier layers prevent direct interaction between adjacent InGaN layers, thereby avoiding reabsorption of emitted photons by neighboring quantum wells while maintaining the overall absorption efficiency of the conversion structure.
4Illumination intensity
If the indium concentration in conversion layers is increased to 25-40% for green or red light conversion, then the emission wavelength shifts to longer wavelengths, but the lattice parameter difference between InGaN and GaN increases causing poor quality emissive layers
Solution Approach 1:
Different regions of the conversion structure have different indium concentrations optimized for their specific functions: the emissive layers have high indium concentration (25-40%) for wavelength conversion, while the barrier layers have low indium concentration for maintaining crystal quality and lattice matching with the substrate.
Solution Approach 2:
The conversion layers are segmented into multiple quantum wells with thin InGaN emissive layers (3 nm thickness) separated by GaN barrier layers. This segmentation allows achieving the required absorption while maintaining material quality, as each thin layer remains within the acceptable indium concentration limit despite the total thickness being large (at least 20 quantum wells).
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration achieves improved light absorption and conversion efficiency without degrading the quality of InGaN, allowing for effective conversion of blue light to green or red light with efficiencies greater than 76% and maintaining semiconductor quality.
Implementation Method 1
the absorption of the blue light emitted by the emission structure is carried out not only by the second emissive layer or layers, but also by the absorption layers of the second barriers which comprise InGaN
Implementation Method 2
a conversion structure configured to convert the light intended to be emitted by the emission structure to at least one second wavelength λ2 different from the first wavelength λ1
Implementation Method 3
during production of the second barriers by epitaxy, these first interlayers carry out a 'reinitialization' of the lattice parameter of the material to be grown, allowing the successive production of several InGaN absorption layers without degradation of the quality of the semiconductor
Implementation Method 4
the conversion efficiencies (ratio of the number of photons absorbed to the number of photons re-emitted at the desired wavelength) obtained being less than 20%
Data Source
Figure 1~2
Figure 3
AI summary
Light-emitting diode (100) comprising: - an emission structure (102) of light at a first wavelength λ1, having a pn junction (106, 108) in which is disposed an active region (110) including a first emissive layer (112) comprising InX1Ga1-X1N disposed between two first barriers (114); - a conversion structure (104) configured to convert the light emitted by the emission structure to a second wavelength different from the first, disposed on the emission structure and comprising a second emissive layer (118) of InX2Ga1-X2N, disposed between two second barriers (120) each comprising several absorption layers (122) of InX3Ga1-X3N separated from each other by an interlayer (124) of GaN; in which the concentrations of indium X1, X2 and X3 are such that 0 < X1 < X2 and Eg(InX2Ga1-X2N) < Eg(InX3Ga1-X3N) ≤ hc/λ1.